JP6932938B2 - Intermediate transfer member and image forming apparatus - Google Patents

Description

The present invention relates to an intermediate transfer member and an image forming apparatus. More specifically, the present invention relates to an intermediate transfer material or the like, which can stabilize the measurement of an optical sensor for detecting the toner concentration and has high durability.

Conventionally, in an intermediate transfer body of an electrophotographic image forming apparatus (hereinafter, also referred to as “image forming apparatus”), a technique of measuring the toner concentration on the intermediate transfer body with an optical sensor is known. In the technique of measuring the toner concentration on the intermediate transfer body with an optical sensor, there are various methods for stabilizing the measurement.
However, in particular, in an intermediate transfer body having a surface layer, it is known that the measurement by the optical sensor becomes unstable due to the interference by the light reflected at the interface between the resin base layer and the surface layer.

For example, Patent Document 1 discloses a technique for dealing with this problem.
Patent Document 1 discloses a technique for stabilizing the measurement of an optical sensor by increasing the specular reflectance of the surface layer. In particular, in the technique disclosed in Patent Document 1, in order to increase this specular reflectance, a filler (for example, having a particle size distribution having a particle size distribution in the range of 5 to 100 nm) of a high refractive index material is used. , Titanium oxide.) Is preferable.
In the method of adjusting the refractive index as disclosed in Patent Document 1, the frequency of light reflection on the surface of the surface layer (that is, the surface opposite to the resin base layer) increases, which is rational to the above problem. It is possible to take measures against.
However, in such a method, the following problems arise when considering that a cured acrylic resin (hereinafter, also simply referred to as “acrylic resin”) is generally used as the material of the surface layer.

Titanium oxide exemplified as the filler in Patent Document 1 has a particularly high refractive index, but the nanoparticles of titanium oxide can absorb UV (ultraviolet) light having a wavelength of 300 to 400 nm, which is suitable for curing an acrylic resin. It is known that it is large and has photocatalytic activity by UV light.
That is, when titanium oxide is contained in the surface layer and UV photocuring is performed,
(1) The initiator cannot sufficiently absorb UV light. (2) Problems such as the photocatalytic reaction competing with the curing reaction occur, and the cross-linking reaction rate of the polymerizable monomer or oligomer forming the acrylic resin decreases, resulting in polymerization. Insufficient or insufficient cross-linking. As a result, the surface layer has a reduced mechanical strength due to cracks and the like. Further, due to the bleeding of the oligomer or the like having insufficient cross-linking, the friction between the blade or the like and the intermediate transfer body increases, and as a result, the torque of the intermediate transfer body becomes defective. Therefore, if UV photocuring is performed when titanium oxide is contained in the surface layer, the durability of the surface layer cannot be sufficiently ensured.

Further, Patent Document 2 discloses a method in which spherical large-diameter particles having a high refractive index (particle size of λ / 2 or more with respect to the wavelength λ of the sensor light) are spread on the surface of the intermediate transfer body.
In the case of the method of arranging a large amount of a material having a large refractive index (titanium oxide, etc.) on the surface as disclosed in Patent Document 2, even if the intermediate transfer body has high durability, the cleaning member or the photoconductor can be used. There is a problem that the wear member is formed, and as a result, the durability of the cleaning member and the photoconductor is lowered.
Further, in the method of laying spherical particles on the surface of the intermediate transfer material, a level of surface roughness derived from the diameter of the spherical particles is generated. As a result, recesses are formed between the spherical particles, and toner external additives and the like are accumulated in the recesses. This accumulation may induce problems such as filming. Therefore, when the technique disclosed in Patent Document 2 is adopted, there is a problem that a strong cleaning mechanism is required so that an external additive or the like does not accumulate in the concave portion, and the device configuration becomes complicated.

Further, Patent Document 3 discloses a method of stabilizing the measurement of the reflected light while suppressing the interference of the reflected light by defining the mirror surface degree of the surface of the resin base layer and roughening the surface.
However, when the surface of the resin base layer is roughened as in Patent Document 3, the surface roughness of the resin base layer changes locally, so that the thickness of the surface layer also changes locally. As a result, the surface layer of the surface layer is roughened. Local changes in reflection intensity on the surface (the surface on which light is incident) can occur. In particular, when a thin (6 μm or less) surface layer is formed by the coating method, the influence of the local change in the reflection intensity caused by roughening the surface of the resin base layer cannot be ignored. As a result, the optical sensor recognizes the locally changed portion of the reflection intensity as an error, and adjusts the image density based on the result of the density measurement including the locally changed reflection intensity. There is a problem of improper adjustment.
In order to avoid such a problem, the variation in surface roughness may be particularly small, but in that case, the surface roughness may be reduced each time according to the deterioration state of the device used for adjusting the surface roughness. It is necessary to change the adjustment conditions of the above, which creates a new problem that production is disadvantageous.

Japanese Unexamined Patent Publication No. 2007-171273 Japanese Unexamined Patent Publication No. 2011-242724 Japanese Unexamined Patent Publication No. 2011-123378

The present invention has been made in view of the above problems and situations, and the problem to be solved is an intermediate transfer body capable of stabilizing the measurement of an optical sensor for detecting the toner concentration and having high durability. Etc. are to be provided.

In the process of examining the cause of the above problem in order to solve the above problems, the present inventor has, for example, in the intermediate transfer body in which the surface layer containing the cured acrylic resin as a main component is provided, the interface between the resin base layer and the surface layer. By reducing the reflected light in the invention, the interference of the reflected light can be suppressed, so that the measurement of the optical sensor for detecting the toner concentration can be stabilized, and the resin is sufficiently cured and has high durability. We have found that we can provide an intermediate transfer member and an image forming apparatus, and have arrived at the present invention.
That is, the above problem according to the present invention is solved by the following means.

1 . An intermediate transfer body used in an image forming apparatus that first transfers a toner image carried on an electrostatic latent image carrier to an intermediate transfer body and then secondarily transfers the toner image from the intermediate transfer body to a recording material. hand,
The intermediate transfer material has an endless belt shape and contains at least a resin base layer and a surface layer.
The surface layer contains a binder resin and composite particles containing a first material and a second material.
The composite particles have a structure in which at least the periphery of the first material is coated with the second material.
The average particle size of the composite particles is in the range of 100 to 300 nm.
As the second material, a conductive material is contained, and the material is contained.
During the refractive index of the first material and n _1, and the refractive index of the second material was n _2, in you and satisfies the following relationships (1) and equation (2) Transcript.
n ₁ ≠ n ₂ ・ ・ ・ Relational expression (1)
0.30 << n ₁ −n ₂ | ・ ・ ・ Relational expression (2)
[In the above formula, the refractive indexes n ₁ and n ₂ are values measured at the same wavelength in the wavelength range of 500 to 800 nm. ]

2 . The intermediate transfer material according to item 1, wherein the conductive material contains any one of tin oxide, zinc oxide and titanium oxide.

3 . When the refractive index n ₃ of the binder resin, the refractive index n ₂ of the first refractive index n ₁ and the second material of the material, satisfy the following equation (3) and equation (4) The intermediate transfer product according to the first or second paragraph.
n ₁ <n ₂ ... relational expression (3)
n ₃ <n ₂ ... relational expression (4)

4 . As the binder resin, at least a polyfunctional (meth) on any one of the first term, characterized by comprising a cured (meth) acrylic resin consisting of structural units derived from acrylic monomers until the third term The intermediate transcript of the description.

5 . The item according to any one of items 1 to 4, wherein the resin contained in the resin base layer as a main component has a refractive index of n _4, and the following relational expression (5) is satisfied. Intermediate transcript.
1.6 ≤ n ₄ ... Relational expression (5)

6 . The intermediate transfer product according to any one of items 1 to 5, wherein the resin contained in the resin base layer as a main component is any one of polyimide, polyphenylene sulfide, and polyamide-imide.

7 . The average thickness of the surface layer, an intermediate transfer member according to any one of the first term, characterized in that at 6μm or less to paragraph 6.

8 . An image forming apparatus that first transfers a toner image carried on an electrostatic latent image carrier to an intermediate transfer body, and then secondarily transfers the toner image from the intermediate transfer body to a recording material.
An intermediate transfer member according to any one of the first term to paragraph 7, the optical sensor selected from among visible light or 1000nm or less of the near-infrared light, detect either the wavelength lambda _1, With
An image forming apparatus comprising a means for measuring the toner concentration on the intermediate transfer body by using the optical sensor.

9 . The image forming apparatus according to item 8 , wherein the average particle size r ₁ of the composite particles and the wavelength λ ₁ satisfy the following relational expression (6).
2 × r ₁ <λ ₁・ ・ ・ relational expression (6)

By the above means of the present invention, it is possible to stabilize the measurement of the optical sensor for detecting the toner concentration, and it is possible to provide an intermediate transfer material or the like having high durability.
Although the mechanism of expression or mechanism of action of the effects of the present invention has not been clarified, it is considered as follows.

The composite particle according to the present invention has two layers, and each layer contains materials having different refractive indexes from each other. Therefore, the number of interfaces at which the light incident in the surface layer is scattered or reflected can be doubled. That is, by adopting the above material, the frequency of scattering or reflection of light can be increased. As a result, the proportion of specularly reflected light that causes light interference can be reduced.

Further, although it is easy for light to pass from the low refractive index medium to the high refractive index medium, in order for the light to pass from the high refractive index medium to the low refractive index medium, the angle does not exceed the critical angle. There is a condition.
If the composite particles according to the present invention are adopted, it is considered that the frequency of light scattering and reflection can be more than doubled even under such conditions. As a result, the proportion of specularly reflected light that causes light interference can be dramatically reduced. That is, according to the present invention, it is considered that the interference due to the light reflected at the interface between the resin base layer and the surface layer does not occur, and the measurement of the optical sensor can be stabilized.

If composite particles using the first material and the second material according to the present invention are adopted, unlike the method disclosed in Patent Document 1 and the like, even when a cured acrylic resin is used for the surface layer. Further, the above effect can be obtained regardless of the refractive index of the resin contained in the resin base layer as the main component.
Further, the surface layer according to the present invention may have a structure containing composite particles inside, and does not need to have a structure disclosed in Patent Document 2 for exposing the particles from the intermediate transfer body. Therefore, the present invention can reduce damage to the photoconductor and the cleaning member as compared with the technique disclosed in Patent Document 2 and the like, and is locally derived from the fact that the intermediate transfer material contains large-diameter particles. Since the number of recesses is reduced, cleaning can be facilitated.

The composite particle according to the present invention has two layers, and each layer contains materials having different refractive indexes from each other. Therefore, unlike the technology disclosed in Patent Document 3 and the like, it is possible to stabilize the measurement of the optical sensor for detecting the toner concentration regardless of the surface roughness and the mirror surface of the resin base layer, and it is durable. It is possible to provide an intermediate transcript having high properties.

When ordinary single-layer particles are added instead of the composite particles according to the present invention, the surface on which light is scattered and reflected is limited to the interface between the resin and the particles in the surface layer. Therefore, it is clear that the effect of stabilizing the measurement of the optical sensor for detecting the toner concentration is not sufficiently exhibited.
If single-layer particles of titanium oxide, which is a material having a particularly large refractive index, are used, it is considered that the effect of scattering and reflecting light is enhanced, and it is possible to stabilize the measurement of the optical sensor. Be done. However, considering that a cured acrylic resin is used as a general binder for the surface layer, there are problems such as deterioration of the durability of the surface layer as described above due to UV absorption of titanium oxide in particular. Occurs.

Schematic diagram showing an example of the layer structure of the intermediate transfer material according to the present invention. Schematic cross-sectional view showing an example of the layer structure of composite particles according to the present invention. Schematic cross-sectional view showing an example of an image forming apparatus using an intermediate transfer member according to the present invention.

The intermediate transfer body of the present invention forms an image in which the toner image carried on the electrostatic latent image carrier is first-transferred to the intermediate transfer body, and then the toner image is secondarily transferred from the intermediate transfer body to a recording material. An intermediate transfer body used in the apparatus, wherein the intermediate transfer body has an endless belt shape and includes at least a resin base layer and a surface layer.
The surface layer contains a binder resin and composite particles containing a first material and a second material.
The composite particles have a structure in which at least the periphery of the first material is coated with the second material.
The average particle size of the composite particles is in the range of 100 to 300 nm.
As the second material, a conductive material is contained, and the material is contained.
When the refractive index of the first material is n ₁ and the refractive index of the second material is n ₂ , the relational expression (1) and the relational expression (2) are satisfied. This feature is a technical feature common to or corresponding to the invention according to each claim. Thereby, the present invention can provide an intermediate transfer material which can stabilize the measurement of the optical sensor for detecting the toner concentration and has high durability.

The embodiments of the present invention, the first refractive index n ₂ of the refractive index n ₁ and the second material of the material, to satisfy the above relational expression (2). As a result, the measurement of the optical sensor can be made more stable.

The embodiments of the present invention, as the second material, you containing a conductive material. As a result, the degree of freedom in designing the intermediate transfer member can be increased.

In an embodiment of the present invention, it is preferable that the conductive material contains any one of tin oxide, zinc oxide and titanium oxide. As a result, the degree of freedom in designing the intermediate transfer material can be further increased, and the effects of the present invention can be more preferably exhibited.

The embodiments of the present invention, the when the refractive index n ₃ of the binder resin, the refractive index n ₂ of the refractive index n ₁ and the second material of the first material, the relational expression (3) And it is preferable to satisfy the relational expression (4). Thereby, the effect of the present invention can be more preferably exhibited.

The embodiments of the present invention, the average particle diameter of the composite particles, Ru der range of 100 to 300 nm. As a result, the effects of the present invention can be more preferably exhibited, and cleaning defects caused by excessive surface roughness can be avoided.

In an embodiment of the present invention, it is preferable that the binder resin contains at least a cured (meth) acrylic resin composed of a structural unit derived from a polyfunctional (meth) acrylic monomer. This makes it possible to obtain a more durable intermediate transfer material.

The embodiments of the present invention, the refractive index of the resin contained as a main component in the resin base layer when the n _4, it is possible to satisfy the relational expression (5). With the intermediate transcript of the present invention, the effect can be suitably exhibited even under such conditions.

In an embodiment of the present invention, it is preferable that the resin contained in the resin base layer as a main component is any one of polyimide, polyphenylene sulfide, and polyamide-imide. As a result, the durability of the intermediate transfer material is further improved, and the effect of the present invention can be obtained for a long period of time.

As an embodiment of the present invention, the average thickness of the surface layer can be 6 μm or less. With the intermediate transfer member of the present invention, it is possible to make the measurement of the optical sensor for detecting the toner concentration more stable even under such conditions.

_{The intermediate transfer body of the present invention includes an optical sensor that detects any wavelength λ 1} selected from visible light or near-infrared light of 1000 nm or less, and the optical concentration on the intermediate transfer body is determined. It can be suitably used for an image forming apparatus having a means for measuring using a sensor. Thereby, the effect of the present invention can be more easily expressed.

As the image forming apparatus, the average particle size r ₁ of the composite particles and the wavelength λ ₁ can satisfy the above relational expression (6). Even under such conditions, the effects of the present invention can be more preferably exhibited.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

<< Outline of the intermediate transcript of the present invention >>
The intermediate transfer body of the present invention forms an image in which a toner image carried on an electrostatic latent image carrier is first-transferred to the intermediate transfer body, and then the toner image is secondarily transferred from the intermediate transfer body to a recording material. An intermediate transfer body used in an apparatus, wherein the intermediate transfer body has an endless belt shape and includes at least a resin base layer and a surface layer, and the surface layer is a binder resin and a first material. And a composite particle containing a second material, and the composite particle has a structure in which at least the periphery of the first material is coated with the second material, and the average particle size of the composite particle is formed. Is in the range of 100 to 300 nm, contains a conductive material as the second material, the refractive index of the first material is n _1, and the refractive index of the second material is n _2. When, the following relational expression (1) and relational expression (2) are satisfied.
n ₁ ≠ n ₂・ ・ ・ Relational expression (1)
0.30 << n ₁ −n ₂ | ・ ・ ・ Relational expression (2)
[In the above formula, the refractive indexes n ₁ and n ₂ are values measured at the same wavelength in the wavelength range of 500 to 800 nm. ]

[Intermediate transcript]
The intermediate transfer material according to the present invention has an endless belt shape and includes at least a resin base layer and a surface layer.
The intermediate transcript according to the present invention will be specifically described with reference to FIG.
FIG. 1 is a diagram showing the configuration of the intermediate transfer body 210.

The intermediate transfer body 210 is an image forming apparatus for primary transfer of a toner image supported on an electrostatic latent image carrier (photoreceptor) and then secondary transfer of the primary transferred toner image to a recording medium. Incorporated in.
Here, in the present invention, the primary transfer means transferring the toner image supported on the electrostatic latent image carrier to the intermediate transfer body. Further, the secondary transfer means that the primary transferred toner image is transferred from the intermediate transfer body to the recording material.

As shown in FIG. 1, the intermediate transfer body 210 has a resin base layer 210a and a surface layer 210b. Further, in the intermediate transfer body 210, the resin base layer 210a is located inside and the surface layer 210b is located outside. An elastic layer 210c made of an elastic body may be provided between the resin base layer 210a and the surface layer 210b. As the elastic layer 210c, a known structure can be used. The intermediate transfer body 210 has an endless belt shape. Here, the "endless belt shape" means, for example, a loop-like shape conceptually (geometrically) formed by connecting both ends of a long sheet-like object. .. The actual shape of the intermediate transfer body 210 is preferably a seamless belt-like or cylindrical shape.
The interface between the resin base layer and the surface layer may be subjected to a treatment for enhancing the adhesiveness. Examples of the treatment for enhancing the adhesiveness include UV light irradiation on the surface of the resin base layer, ozone exposure, corona discharge treatment, and the like, but the treatment is not limited to these methods, and one or a plurality of known methods may be used. It can be selected and implemented.

<Resin base layer>
The resin base layer is made of resin, and can be appropriately selected from resins that do not undergo modification or deformation within the operating temperature range of the intermediate transfer material. Examples of the resin used include polycarbonate, polyphenylene sulfide (hereinafter, also referred to as “PPS”), polyvinylidene fluoride, polyimide (hereinafter, also referred to as “PI”), and polyamideimide (hereinafter, also referred to as “PAI”). ), Polyalkylene terephthalate (polyethylene terephthalate, polybutylene terephthalate, etc.), polyether, polyetherketone, polyetheretherketone, ethylenetetrafluoroethylene copolymer, polyamide, etc. are included. From the viewpoint of heat resistance and strength, the resin preferably contains polyimide, polycarbonate, polyphenylene sulfide and polyalkylene terephthalate, and more preferably contains polyphenylene sulfide or polyimide. Polyimide can be obtained by heating polyamic acid, which is a precursor of polyimide. Further, the polyamic acid can be obtained by dissolving a tetracarboxylic dianhydride or a substantially equimolar mixture of a derivative thereof and a diamine in an organic polar solvent and reacting them in a solution state. When polyimide is used for the resin base layer, the content of polyimide in the resin base layer is preferably 51% by mass or more.

The resin contained in the resin base layer as a main component is preferably any of polyimide, polyphenylene sulfide, and polyamide-imide. The resin contained in the resin base layer as a main component means a resin that occupies 51 parts by volume or more in 100 parts by volume of the resin base layer. Polyimide, polyphenylene sulfide, and polyamide-imide are typical examples of the material of the resin base layer, but since these resins are materials having excellent mechanical strength, the durability is further improved and the effect of the present invention can be obtained for a long period of time. be able to.

Further, as the material of the resin base layer, an elastic body similar to that that can be used for the elastic layer can be contained. If the material of the resin base layer is an elastic body, it is advantageous in ensuring the performance of secondary transfer to various recording media. That is, if the material of the resin base layer has elasticity, even when a recording medium having a large surface roughness or surface unevenness such as rough paper is used as the recording medium, it can be applied to all surfaces regardless of the unevenness of the paper. Since it is possible to follow, good secondary transferability without defects can be obtained.

The resin substrate is preferably an electrical resistance value (volume resistivity) is in the range of ¹⁰ 5 ^{~10 12 Ω} · cm. In order to keep the electric resistance value of the resin base layer within a predetermined range, the resin base layer may contain, for example, a conductive substance. Examples of conductive substances include carbon black and the like. As the carbon black, neutral or acidic carbon black can be used. The conductive substance varies depending on the type of the conductive substance, but may be added so that the volume resistivity and the surface resistance value of the intermediate transfer material are within a predetermined range. Usually, it may be added in the range of 5 to 75 parts by volume with respect to 100 parts by volume of the resin, and preferably it may be added in the range of 10 to 40 parts by volume with respect to 100 parts by volume of the resin.

The thickness of the resin base layer is preferably in the range of 50 to 200 μm. Further, various known additives may be added to the resin base layer as long as the effects of the present invention are not impaired. Examples of additives include dispersants such as nylon resin.

The resin base layer can be produced by a conventionally known general method. For example, the resin base layer can be manufactured into an annular shape (endless belt shape) by melting a heat-resistant resin as a material by an extruder, forming it into a tubular shape by an inflation method using an annular die, and then cutting it into round slices.

<Surface layer>
The surface layer according to the present invention contains a binder resin and composite particles containing a first material and a second material.

<Bundling resin>
As the binder resin according to the present invention, a known resin used for the surface layer of the intermediate transfer material can be used, but a cured (meth) acrylic resin is preferable.

Above all, as the binder resin according to the present invention, it is preferable to contain at least a cured (meth) acrylic resin composed of a structural unit derived from a polyfunctional (meth) acrylic monomer.
Since the cured (meth) acrylic resin composed of such constituent units can be synthesized by a curing (polymerization) reaction at a low temperature, a surface layer having excellent mechanical strength and durability can be obtained without damaging the resin base layer. It can be formed, and thus can be a more durable intermediate transfer material.

(Curing (meth) acrylic resin)
Here, the "cured (meth) acrylic resin" according to the present invention is other than the (meth) acrylic resin (so-called "UV curable resin") cured by irradiation with active light such as ultraviolet rays (UV) and irradiation with active light. Contains (meth) acrylic resin cured by the means of. Such a (meth) acrylic resin generally means a polymer of an acrylic acid ester or a methacrylic acid ester, but the present invention is not limited to this, and an acryloyl group or a methacrylic acid group is polymerized. It shall include a wide range of structures.

Further, "(meth) acrylic" means "acrylic or methacryl". Therefore, "(meth) acrylic resin" means "acrylic resin or methacrylic resin", and "(meth) acrylic monomer" means "acrylic monomer or methacrylic monomer". Similarly, "(meth) acryloyl" means "acryloyl or methacryloyl", and thus "(meth) acryloyl group" means "acryloyl group or methacryloyl group".

As the cured (meth) acrylic resin, a cured (meth) acrylic resin using or using a tetrafunctional or higher functional monomer is particularly preferable. Examples of the tetrafunctional or higher functional monomers include, but are not limited to, the following monomers 1 to 3. In the monomer 3, n is preferably 1 to 5.

Since the cured (meth) acrylic resin using a tetrafunctional or higher functional monomer in combination is a resin that can be cured by light or an electron beam, it can be cured under mild conditions. Therefore, it is preferable that the intermediate transfer material can be easily produced, such as forming a surface layer. The durability of the tetrafunctional or higher functional monomers used can be further improved by increasing the number of functionals.

(Thickness of surface layer)
The average thickness of the surface layer (hereinafter, also simply referred to as “thickness”) is preferably 6 μm or less.
Generally, if the average thickness of the surface layer is 6 μm or less, it is a condition that interference of reflected light is likely to occur at the interface between the surface layer and the resin base layer. Conceivable.
However, in the present invention, since the surface layer contains the above-mentioned composite particles, it is possible to stabilize the measurement of the optical sensor for detecting the toner concentration even if the surface layer has a thickness of 6 μm or less. In the surface layer having an average thickness of 6 μm or less, it is difficult to form a uniform surface layer when large-diameter particles are added, but the composite particles according to the present invention need to be large-diameter particles. It is easy to form a uniform surface layer, and it is possible to make the measurement of the optical sensor for detecting the toner concentration more stable.

The thickness of the surface layer is preferably 0.5 μm or more, more preferably 1 μm or more. If it is 0.5 μm or more, it is possible to prevent scratches generated on the surface layer from penetrating to the resin base layer.
Further, in order to form a surface layer having a uniform thickness, it is considered that the thickness is at least 5 times or more the particle size of the composite particles, preferably 10 times or more the particle size. Even in view of the fact, the composite particles according to the present invention, from the particle size is within the range of 100 to 300 nm, the average thickness of the surface layer is preferably 0.5μm or more.

(Measuring method of surface layer thickness)
The thickness of the surface layer can be measured using a known method / apparatus, for example, using an eddy current type film thickness measuring device “EDDY560C” (manufactured by HELMUT FISCHER GmbH CO). ..
The average thickness of the surface layer is obtained by randomly measuring the thickness of 10 or more places and taking the average.

<Curing method of resin constituting the surface layer>
As a method for curing the resin constituting the surface layer (method for polymerizing and cross-linking the monomer), curing by energy rays is preferable, and curing by UV (hereinafter, also referred to as “UV curing”) is preferable. UV curing is preferable in terms of production of an intermediate transfer material because it does not require heat treatment or cooling treatment, and does not require selection of a material or design of an apparatus in consideration of the difference in thermal expansion coefficient.

Generally, when UV curing is performed, a photopolymerization initiator is used in combination.
Known photopolymerization initiators can be used, but from the viewpoint of curing (that is, monomer polymerization and cross-linking) efficiency, photopolymerization initiators having an acylphosphine oxide-based or oxime ester-based skeleton can be used. preferable. As the photopolymerization initiator having an acylphosphine oxide-based skeleton, a commercially available product can be used, and for example, Irgacure TPO, Irgacure 819 and the like can be used. As the photopolymerization initiator having an oxime ester-based skeleton, a commercially available product can be used, and for example, Irgacure OXE02, Irgacure OXE01 and the like can be used.

In addition to the above photopolymerization initiator, an additive (tertiary amine or the like) for increasing the reaction rate of UV curing may be used. As the additive, a commercially available product can be preferably used, and examples thereof include KAYACURE EPA manufactured by Nippon Kayaku Co., Ltd.
The UV light source is not particularly limited, but preferably has a main emission at 300 to 400 nm.
In the case of electron beam curing, a photopolymerization initiator is not required.

<Composite particles>
The composite particle according to the present invention has a structure in which at least the periphery of the first material is coated with the second material.
The mode of the composite particles is not particularly limited, and may be, for example, a spherical shape having a core-shell structure, or particles made of a second material may surround the particles containing the first material. It may be configured to cover.
A specific example of the cross-sectional shape of the composite particle 100 according to the present invention is shown in FIG. In FIG. 2, 110 is the first material and 120 is the second material.

The coating around the particles containing the first material by the shell or particles made of the second material may be a mode in which the surface of the particles containing the first material is evenly and continuously covered so as not to be exposed at all. Alternatively, the surface may be discontinuously coated so that the surface of the particles containing the first material is partially exposed. That is, the rate of covering the periphery of the particles containing the first material does not necessarily have to be 100%, and is preferably 50% or more.
The particle size of the particles containing the first material is preferably at least 40 nm or more. This is because when the particle size of the particles containing the first material is 40 nm or more, the effects of scattering, reflecting and refracting light can be sufficiently exhibited. The particle size of the particles containing the first material is preferably 270 nm or less in consideration of the thickness of the second material in the composite particles.
The thickness (or the particle size of the second material, if the second material forms particles) of the second material that covers the periphery of the particles containing the first material may be 30 nm or more. preferable. This is because when the particle size of the particles containing the second material is 30 nm or more, the effects of scattering, reflecting and refracting light can be sufficiently exhibited.

The particle size of the particles containing the first material can be measured in the same manner as the measurement of the particle size of the composite particles.
Further, the thickness of the second material that covers the periphery of the particles containing the first material is assumed to be obtained by subtracting the particle size of the particles containing the first material from the particle size of the composite particles.

(First material)
The first material according to the present invention is not particularly limited as long as it is a material satisfying the relational expression (1), but it is preferable that the material can maintain its shape in the surface layer.
For example, hollow particles in which the first material is a gas such as air and the inside is air (gas) may be formed as composite particles. In this case, as the second material, it is preferable to use a material that imparts rigidity and strength to the outside of the first material.
Even when the first material is a material other than gas and the composite particles are two-layer particles other than hollow particles, the first material is not particularly limited, but the composite described below is used. In view of a general method for producing particles (a method of coating the periphery of a first material with a second material), the first material may be preferable to some extent.

Here, as a method of coating the periphery of the first material with the second material, a method relating to the formation of a chemical film, a sol-gel formation reaction using an organometallic compound as a raw material, MOCVD: Metalorganic Chemical Vapor Deposition (organic). Known methods such as a metal-chemical vapor deposition (metal-chemical vapor deposition) method and an ALD (atomic layer deposition) method can be mentioned. However, in each method, heating must be performed in the supply stage of the precursor (raw material) for forming the second material, the dehydration step immediately before the surface modification, and the final treatment. As the material of, it is preferable that it can withstand heating and physical friction during reaction.
Therefore, considering that the composite particles may be heated when they are produced, for example, when the composite particles are produced by adopting a sol-gelling reaction, a material that can withstand an environment of 150 ° C. or higher. Is preferable. Further, when composite particles are produced by adopting a general firing treatment, it is preferable that the material can withstand an environment of 500 ° C. or higher.
Considering heat resistance, it is preferable to use an inorganic substance as the solid first material.

For the above reasons, typical inorganic materials that can be used as the first material include, for example, barium titanate, silica, alumina, aluminum borate, barium sulfate, calcium carbonate, zirconium oxide, and fluoride. Examples include, but are not limited to, magnesium, cerium oxide, tin oxide, zinc oxide, titanium oxide and the like.

(Second material)
The second material according to the present invention is not particularly limited as long as it satisfies the relational expression (1), but preferably contains a known conductive material, and specifically, for example, tin oxide. , Zinc oxide, titanium oxide, ITO and other known conductive materials are preferably contained.
If the second material contained in the surface of the composite particles is a conductive material, the composite particles can be used as the conductive material, so that the electrical resistance of the surface layer can be easily adjusted. As a result, a large amount of composite particles can be mixed in the surface layer. As described above, when the second material is a conductive material, the degree of freedom in designing the intermediate transfer body can be increased, which is preferable.
There is no particular problem even if a material other than the conductive material is applied as the second material, but in the case of such a material, a mechanical load is applied during the dispersion treatment in the case of producing the intermediate transfer material. It is preferable that the resin has an inorganic oxide or a crosslinked structure because it needs to withstand the above.

As described above, the second material according to the present invention preferably contains any of tin oxide, zinc oxide and titanium oxide as the conductive material, but the most preferable of these. Is tin oxide, then preferably zinc oxide, then preferably titanium oxide. Tin oxide has lower photocatalytic activity and UV absorption than zinc oxide and titanium oxide, and can be suitably contained in a surface layer using an acrylic resin that is cured using UV. Since zinc oxide has a small photocatalytic activity, it can be suitably contained in the surface layer.
If a conductive material is used as the second material, the electrical resistance of the surface layer can be adjusted particularly easily, so that the degree of freedom in designing the intermediate transfer body can be further increased, and the present invention also provides. The effect of can be more preferably expressed.

<Manufacturing method of composite particles>
The method of coating the periphery of the first material with the second material is not particularly limited, and for example, as described above, a method relating to the formation of a chemical film, a sol-gelling reaction using an organometallic compound as a raw material, and the like. Known methods such as the MOCVD method and the ALD method can be mentioned. In addition to these, a method in which the first material is dispersed in water and then immersed in a dispersion liquid or solution of the second material can be mentioned. As the dipping method, a known method can be used, and for example, JP-A-6-192592, JP-A-6-299086, JP-A-2015-090824, JP-A-2014-59993, etc. The method described in can be used.

<Surface modification of composite particles>
For the purpose of improving the dispersibility of the composite particles and improving the physical characteristics of the surface layer after completion, surface modifiers such as various coupling agents (so-called "surface treatment agents") are used for the composite particles. The surface may be modified. A known method can be used for surface modification, but a coupling agent having a (meth) acryloyl group is particularly preferable because the mechanical strength of the surface layer is further improved.

Other examples of the surface modifier include the compounds described in paragraphs 0075 to 0077 of JP2013-24898A, and commercially available products include 3-acryloxypropyltrimethoxysilane (KBM-5103; Shin-Etsu Chemical Co., Ltd.). (Industrial Co., Ltd.), but the present invention is not limited to these, and known compounds can be used.
As the surface modification method, for example, the method described in paragraphs 0080 to 985 of JP2013-24898A can be used.

<Average particle size of composite particles>
The average particle size of the composite particles, Ru der range of 100 to 300 nm.
Average particle size in der Rukoto above 100 nm, the effect of the present invention is Ru exhibited.
The average particle size of below der Rukoto 300 nm, dispersibility productivity is increased due to easier to coating solution also can the surface roughness of the surface layer suitably, the surface roughness becomes excessive It is possible to avoid cleaning defects caused by the above.
Further, the value (inner diameter / particle size) of the ratio of the particle size (hereinafter, also referred to as the inner diameter) of the particles containing the first material to the particle size of the composite particles is within the range of 1/4 to 7/10. Is preferable. Within this range, it is possible to prevent the distance through which light can pass from becoming excessively small, and it is possible to preferably generate scattering, reflection, and refraction of light.

(Measuring method of average particle size of composite particles)
_{First, let r 0} be the average value of the maximum diameter and the minimum diameter (that is, (maximum diameter + minimum diameter) / 2) in one composite particle.
Next, 100 composite particles are randomly extracted from the observation field of view under an electron microscope. Then, the above value r ₀ is calculated for 100 composite particles, and the average value of the values r ₀ is defined as the average particle size r ₁ of the composite particles.

[Relationship of refractive index]
<Relationship between the refractive index of the first material and the second material>
In the present invention, when the refractive index of the first material is n ₁ and the refractive index of the second material is n ₂ , the following relational expression (1) is satisfied.
n ₁ ≠ n ₂・ ・ ・ Relational expression (1)
[In the above formula, the refractive indexes n ₁ and n ₂ are values measured at the same wavelength in the wavelength range of 500 to 800 nm. ]

Refractive index n ₂ of the refractive index n ₁ and the second material of the first material further satisfying the lower Symbol relational expression (2).
0 . 30 << n ₁ −n ₂ | ・ ・ ・ Relational expression (2)
By defining a large difference in refractive index, the effect (frequency) of scattering and reflecting light can be further enhanced, so that the measurement of the optical sensor can be made more stable.

When there is no difference in refractive index (when n ₁ = n ₂ ), light is not suitably scattered or reflected at the interface between the layers even if the material has a two-layer structure. The larger the refractive index difference (| n ₁ −n ₂ |) is, the more preferable it is. However, in the case of a design that greatly exceeds 1, it becomes difficult to prepare particles or design an intermediate transfer body using the completed particles. Considering the ease of handling, a particularly preferable upper limit of _{| n 1 −} n _{2 | is 0.8.}

<Relationship between the binder resin, the first material, and the refractive index n _{2 of the second material>}
When the refractive index n ₃ of the binder resin, the refractive index n ₂ of the refractive index n ₁ and a second material of the first material, it is preferable to satisfy the following equation (3) and equation (4) ..
n ₁ <n ₂ ... relational expression (3)
n ₃ <n ₂ ... relational expression (4)
In the case of a surface layer containing a plurality of types of binder resin (resin contained in the surface layer), if the resins are mixed with each other, the average value of the refractive index is calculated based on the blending ratio. It should be _3. In the case of immiscible resins, the refractive index of the resin used as the main component may be _{the refractive index n 3 of the binder resin.}

By satisfying the above relational expressions (3) and (4), n ₂ takes a larger value than n ₁ and n _3. That is, all the materials adjacent to the second material have a lower refractive index than the second material.
With such a relationship of refraction, when light is incident during measurement, the light travels in the order of a material with a small refraction, a material with a large refraction, a material with a small refraction, and a material with a large refraction. Therefore, it is possible to frequently generate a specific critical angle condition in which the refracted light is emitted after the critical reflection is repeated once or a plurality of times. As a result, the probability that the light that has entered the outer layer (second material) of the composite particle is critically reflected is further increased, and as a result, the probability that the light reaches the surface of the resin base layer is reduced. , The proportion of specularly reflected light that causes light interference can be dramatically reduced, and the effect of the invention can be enhanced.
In addition, n ₃ has a refractive index of 1.7 and PAI of 1.6 or more, which are preferably used as a resin contained in the resin base layer as a main component, and thus is 1.6 or more. Is considered to be common, but not limited to this.

<Refractive index of resin contained in the resin base layer as the main component>
When the refractive index of the resin contained in the resin base layer as the main component is n ₄ , it is preferable that the following relational expression (5) is satisfied.
1.6 ≤ n ₄ ... Relational expression (5)
The upper limit of n ₄ is not particularly limited, but the upper limit of _{n 4 is 1.8 in view of the commonly used resin.}

When the resin contained as the main component in the resin base layer has a high refractive index, light is inevitably easily reflected at the interface between the surface layer and the resin base layer, and is reflected at the interface between the resin base layer and the surface layer. Since light easily interferes with each other, it is generally difficult to stabilize the measurement with an optical sensor.
However, with the intermediate transfer material of the present invention, even under such conditions, it is possible to reduce the reflection of light at the interface between the resin base layer and the surface layer, and as a result, the reflected light interferes. Since it can be suppressed, the effect of stabilizing the measurement of the optical sensor for detecting the toner concentration can be suitably exhibited.

<Measurement method of refractive index>
As a method for measuring the refractive index, measurement of the refractive index by an ellipsometry method can be preferably used. Specifically, the refractive index can be obtained by irradiating a measurement sample having a wavelength of 632.8 nm with a laser beam and measuring it using an ellipsometer.

The principle of measuring the refractive index by ellipsometry will be briefly described below.
As the sample of this method, a thin film (thickness of 50 nm to 2 μm) of the measurement sample is formed on a translucent substrate whose refractive index is known and whose refractive index difference is clear.
In ellipsometry, a sample is irradiated with polarized light and the change in polarized light between incident light and reflected light is measured.
This change is
Phase difference between s-polarized light and p-polarized light: Δ
Reflection amplitude ratio of s-polarized light and p-polarized light: tanΨ
It is defined as, and is usually expressed as Δ, Ψ.
(Ψ, Δ) changes depending on parameters such as wavelength (λ), incident angle (φ), sample film thickness (d), and optical constant of the substance (complex refractive index: N or complex permittivity: E).
Once (Ψ, Δ) is obtained, the film thickness (d) and the optical constant (N or E) of the substance can be calculated from this.

From the complex refractive index and the complex dielectric constant, the refractive index (n) and the extinction coefficient (k) of each layer can be finally obtained through the following formula (A).

Equation (A)
N = n + ik
E = ε _r + iε _i

In the above equation (A), ε _r is a vacuum permittivity and ε _i is an imaginary value of the permittivity.
There are two known detailed measurement methods of the ellipsometry method, the rotary photon method and the phase modulation method, but in the present invention, any method may be used.

The refractive index is determined by the refractive index list (URL: http: //www.filmetricsinc.jp/refractive-index-database) disclosed by Filmometrics Co., Ltd. N. Publicly available numbers such as Polyansky and Refractive index database (URL: http: // Refractive index.info.) Can also be used.

[Image forming device]
The image forming apparatus according to the present invention primary transfers the toner image carried on the electrostatic latent image carrier to the intermediate transfer body, and then secondarily transfers the toner image from the intermediate transfer body to the recording material.
_{Further, the image forming apparatus according to the present invention includes an optical sensor that detects any wavelength λ 1} selected from visible light or near-infrared light of 1000 nm or less, and further, the toner concentration on the intermediate transfer body. It is preferable to have a means for measuring the light using the optical sensor. As a result, the detectability of the toner concentration measurement on the intermediate transfer material is stabilized, so that the effect of the present invention can be more easily exhibited.
The details of the image forming apparatus according to the present invention will be described below.

FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the image forming apparatus according to the present invention.
This image forming apparatus is a so-called tandem type color image forming apparatus, and includes four sets of image forming units 10Y, 10M, 10C, 10Bk, an intermediate transfer body unit 7, and a secondary transfer roller 5b as a secondary transfer means. And the paper feed transporting means 21 and the fixing means 24. A document image reading device SC is arranged above the main body A of the image forming device.

The image forming unit 10Y forms a yellow image, the image forming unit 10M forms a magenta image, and the image forming unit 10C forms a cyan image, and forms an image. The unit 10Bk forms a black image.

The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of the toner images formed on the photoconductors 1Y, 1M, 1C, and 1Bk are different from each other. A detailed description will be given using 10Y as an example.

The image forming unit 10Y has a charging means 2Y, an exposure means 3Y, a toner image forming means 4Y, a primary transfer roller 5Y as a primary transfer means, and a cleaning means 6Y around a drum-shaped photoconductor 1Y as an image carrier. Is arranged to form a yellow (Y) toner image on the photoconductor 1Y. Further, in the present embodiment, at least the photoconductor 1Y, the charging means 2Y, the toner image forming means 4Y, and the cleaning means 6Y are integrally provided in the image forming unit 10Y.

The photoconductor 1Y is rotationally driven in the direction of the arrow in FIG. 3 at a predetermined peripheral speed.
In the rotation process, the photoconductor 1Y is uniformly charged to a predetermined polarity and potential by the charging means 2Y, and then image exposure by scanning exposure or the like with a laser beam modulated in response to a digital image signal by the exposure means 3Y. By receiving the above, an electrostatic latent image corresponding to the color component image (color information) of the target yellow image is formed.

The charging means 2Y applies a uniform potential to the photoconductor 1Y, and in the present embodiment, a corona discharge type charger is used for the photoconductor 1Y.

The exposure means 3Y exposes the photoconductor 1Y to which a uniform potential is applied by the charging means 2Y based on a digital image signal (yellow image signal) to form an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, an exposure unit 3Y composed of LEDs and imaging elements in which light emitting elements are arranged in an array in the axial direction of the photoconductor 1Y, a laser optical system, or the like is used.

The toner image forming means 4Y is provided with a rotating developing sleeve, and the toner held on the developing sleeve is conveyed to the surface of the photoconductor 1Y to make an electrostatic latent image manifest, thereby forming a toner image. Yes, known ones can be used.

The primary transfer roller 5Y transfers the toner image formed by the toner image forming means 4Y to the surface of the intermediate transfer body 70 that moves in the same direction as the photoconductor 1Y at a position where it comes into contact with the photoconductor 1Y. And known ones can be used.

The cleaning means 6Y comprises, for example, a rubber blade that removes the toner remaining on the photoconductor 1Y after the toner image is transferred to the intermediate transfer body 70.

The intermediate transfer unit 7 has an endless belt-shaped intermediate transfer 70 wound and rotatably supported by a plurality of rollers 71, 72, 73, 74. In the image forming apparatus according to the present invention, it is preferable to use the intermediate transfer member of the present invention as the intermediate transfer member 70.
The intermediate transfer body 70 is rotationally driven at a predetermined peripheral speed in the direction of the arrow in FIG. 3, that is, in the direction of moving in the same direction as the photoconductor 1Y at the position where it comes into contact with the photoconductor 1Y.

The secondary transfer roller 5b as the secondary transfer means transfers the toner image on the intermediate transfer body 70 onto the recording material P conveyed from the paper feed cassette 20 at a predetermined timing, and a known one is used. be able to.
The recording material may be any material as long as the toner image can be transferred, and examples thereof include a resin sheet and sheet-shaped paper.

The fixing means 24 heats and pressurizes the toner image transferred onto the recording material P by the secondary transfer roller 5b with a pair of rollers to fix the toner image on the recording material P, and is known. Can be used.

During the image forming process, the primary transfer roller 5Y is always in contact with the photoconductor 1Bk via the intermediate transfer body 70. The other primary transfer rollers 5Y, 5M, 5C come into contact with the corresponding photoconductors 1Y, 1M, 1C via the intermediate transfer body 70 only when forming a color image.
The secondary transfer roller 5b comes into contact with the intermediate transfer body 70 only when the recording material P passes through and the secondary transfer is performed.

Further, the housing 8 can be pulled out from the device main body A via the support rails 82L and 82R.

In such an image forming apparatus, in the image forming units 10Y, 10M, 10C, 10Bk, the photoconductors 1Y, 1M, 1C, 1Bk are charged by the charging means 2Y, 2M, 2C, 2Bk, and the exposure means 3Y, 3M. , 3C, 3Bk exposes, toner image forming means 4Y, 4M, 4C, 4Bk develops to form toner images of each color, and primary transfer rollers 5Y, 5M, 5C, 5Bk form the toner images of each color on the intermediate transfer body 70. The toner images are sequentially superimposed and transferred. Then, the recording material P housed in the paper feed cassette 20 is fed by the paper feed transport means 21, passes through the plurality of intermediate rollers 22A, 22B, 22C, 22D, and the resist roller 23, and becomes the secondary transfer roller 5b. At the same time as being conveyed, the color toner image transferred onto the intermediate transfer body 70 is collectively transferred onto the recording material P. After that, the color toner image transferred onto the recording material P is fixed by pressurization and heating in the fixing means 24, and the recording material P on which the color toner image is fixed is sandwiched between the paper ejection rollers 25 to eject paper outside the machine. It is placed on the tray 26. After the toner image is transferred to the intermediate transfer body 70, the photoconductors 1Y, 1M, 1C, 1Bk are subjected to the following after cleaning the toner left on the photoconductor by the cleaning means 6Y, 6M, 6C, 6Bk. Used for image formation.
On the other hand, after the color toner image is transferred onto the recording material P by the secondary transfer roller 5b, the residual toner is removed from the intermediate transfer body 70 whose curvature is separated from the recording material P by the cleaning device 6A.

<Optical sensor>
The optical sensor (not shown) according to the present invention detects _{any wavelength λ 1} selected from visible light or near-infrared light of 1000 nm or less.
As a result, the optical sensor according to the present invention detects the toner concentration (toner adhesion amount) on the intermediate transfer member 70. As the optical sensor, a known one can be used, and specifically, for example, an IDC sensor (Image Density Control Sensor) or the like can be used.
The optical sensor is preferably a means (not shown) for measuring the toner concentration on the intermediate transfer body using the optical sensor. Specifically, for example, optical sensors are provided on the front side and the back side in the direction perpendicular to the recording material P on the downstream side of the primary transfer roller 5Bk and on the upstream side of the secondary transfer roller 5b, respectively, and toner. It is preferable to detect the amount of toner adhered to the front side portion and the back side portion of the image, respectively.

The preferable wavelength range of visible light detected by the optical sensor is in the range of 400 to 1000 nm, and more preferably in the range of 600 to 1000 nm. With such an optical sensor, the optical sensor can be easily obtained, and the accuracy is not excessively high, so that the toner concentration of each color can be sufficiently detected.

According to the configuration of the present invention, the average particle size r ₁ and the wavelength λ _{1 of the} composite particles can satisfy the following relational expression (6). Under such conditions, the particle size is less than half of the wavelength λ detected by the sensor, so that the effect of scattering light is small in the prior art.
However, the composite particles according to the present invention are bilayered with materials having different refractive indexes. Therefore, even when the relational expression (6) is satisfied, the effect of scattering and reflecting light can be improved, and as a result, the proportion of specularly reflected light that causes interference can be reduced. As a result, the effect of the present invention can be sufficiently obtained.
2 × r ₁ <λ ₁・ ・ ・ relational expression (6)
By using particles having a small particle size that satisfy the relational expression (6), the particles can be easily dispersed in the coating liquid for forming the surface layer, and the thickness of the surface layer can be reduced. However, it can also be preferable in terms of design.

The embodiment to which the present invention can be applied is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.

For example, in the above, the composite particles according to the present invention have been described by taking as an example particles having a two-layer structure of a first material and a second material, but the composite particles according to the present invention are limited to this. However, it may have a structure of three or more layers.
Further, in the surface layer, Ru contain a conductive material in addition to the composite particles. In addition to adopting the composite particles according to the present invention as such a conductive material, a known conductive material may be contained. Such known conductive materials are not particularly limited, but are known, for example, ITO (indium-tin composite oxide), tin oxide, zinc oxide, titanium oxide, carbon black, carbon nanotubes, graphene, and the like. One or more kinds of particles made of a conductive material (conductive particles) may be used or used in combination, and may be added in a manner different from that of the composite particles according to the present invention.
Further, the surface layer according to the present invention contains, if necessary, other materials (for example, known antioxidants) in addition to the above-mentioned materials as long as the effects of the present invention are not impaired. You may be doing it.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the indication of "parts" or "%" is used, but unless otherwise specified, it indicates "parts by mass" or "% by mass".

[Preparation of Particles 1 to 7, Particles 11 to 13]
Particles 1 to 7 and particles 11 to 13 were produced as follows. The particles 1 to 7 and 11 were composite particles having a core-shell structure in which the periphery of the core portion (particle) containing the core material was covered with a shell made of a shell material. The core-shell structure was confirmed by determining the element ratio between the central portion and the surface layer portion of each particle from the analysis by energy dispersive spectroscopy and X-ray photoelectron spectroscopy using a high-resolution transmission electron microscope.

<Preparation of particle 1 (first material (hereinafter, also referred to as "core material") = aluminum borate, second material (hereinafter, also referred to as "shell material") = tin oxide)>
100 g of aluminum borate particles having an average particle size of 0.1 μm were suspended in 300 mL of water at 25 ° C. Then, 50 g of a 50% NaOH aqueous solution was added, and then 75.8 g of Na ₂ [Sn (OH) ₆ ] dissolved in 200 mL of water was added. Stirring was continued for 30 minutes to evenly disperse all components in the suspension. Then, dilute sulfuric acid was added dropwise over 3 hours to lower the pH to 3.0 (liquid temperature 25 ° C.) to precipitate a layer of hydrated tin dioxide on the aluminum borate particles. Further, the suspension was kept at the above pH for 5 hours while stirring for aging. Then, the solid matter was separated by filtration, washed with water, dried in a dryer, and calcined at 900 ° C. in a muffle furnace to prepare particles 1.

<Preparation of particles 2 (core material = aluminum borate, shell material = zinc oxide)>
Using an atomic layer deposition system (Beneq equipment TFS200), the surface of aluminum borate, which is a core material thinly spread in a powder tray, was coated with zinc oxide as follows.

First, the powder of the core material is inserted into the powder tray inside the vacuum chamber.
Next, the inside of the vacuum chamber was exhausted by a pump to 5 Pa (hereinafter referred to as "atmospheric pressure after exhaust"), and then the powder was heated to 300 ° C. by a heater. This temperature was maintained for 1 hour to remove adsorbed water and adsorbed gas.

Then, in order to form a coating layer, the following four-step process of the atomic layer deposition method was repeated until the desired particle size was obtained.

Next, in order to form a further coating layer on the outside of the coating layer, the raw material gas 1 and the raw material gas 2 are further repeated by the four-step process of the following atomic layer deposition method, and the layers are sequentially deposited to obtain the thickness of zinc oxide. After the film formation was completed, the vacuum chamber was opened to atmospheric pressure to prepare particles 2 having the average particle size of the completed particles shown in Table I.

-Four-step process of atomic layer deposition-
1st step: Put the gas of the raw material gas 1 into the reaction chamber 2nd step: Exhaust unnecessary gas excess in the reaction chamber 3rd step: Put the gas of the raw material gas 2 into the reaction chamber 4th step: Put the gas of the raw material gas 2 into the reaction chamber Exhaust unnecessary gas in the above
The raw material gas 1 (metal element source) is diethylzinc (manufactured by Sigma-Aldrich).
The raw material gas 2 (oxygen element source) is H ₂ O (manufactured by Sigma-Aldrich).
The generation temperature of each raw material gas was set to 150 ° C.

<Preparation of particles 3 (core material = barium sulfate, shell material = tin oxide)>
100 g of barium sulfate having an average particle size of 0.1 μm was suspended in 300 mL of water at 25 ° C. Then, 50 g of a 50 mass% NaOH aqueous solution was added, and then 75.8 g of Na ₂ [Sn (OH) ₆ ] dissolved in 200 mL of water was added. Stirring was continued for 30 minutes to evenly disperse all components in the suspension. Then, 20% by mass dilute sulfuric acid was added dropwise over 3 hours to lower the pH to 2.5 to precipitate a layer of hydrated tin dioxide on the particles. Further, the suspension was kept at the above pH for 4 hours while stirring for aging. After washing until the conductivity became 300 μS / cm or less, nutche filtration was performed to obtain a cake. Then, it was dried in a drier and fired in a muffle furnace at 900 ° C. for 40 minutes to prepare particles 3.

<Preparation of particles 4 (core material = alumina, shell material = titanium oxide)>
In the preparation of the particles 2, the average particle size of the core portion and the desired average particle size shown in Table I (Table I shows "Average particle size r _{1 of the finished particles", except that the conditions were changed as follows.} The film was formed until the particles 4 were obtained.
Core material: Alumina Pressure after exhaust: 2Pa
Raw material gas 1: Tetrakis (dimethylamide) titanium (IV) (manufactured by Aldrich)
Raw material gas 2: H ₂ O (manufactured by Aldrich)
Raw material gas generation temperature: 180 ° C

<Preparation of particles 5 (core material = barium titanate, shell material = tin oxide)>
In the preparation of the particles 2, the conditions were changed as follows, and the same as the preparation of the particles 2 except that the average particle diameter of the core portion and the average particle diameter r ₁ of the completed particles shown in Table I were obtained. To obtain particles 5.
Core material: Barium titanate Raw material gas 1: Tetrakis (dimethylamide) tin (IV) (manufactured by Aldrich)
Raw material gas 2: H ₂ O (manufactured by Aldrich)
Raw material gas generation temperature: 160 ° C

<Particle 6 (core material = air, shell material = crosslinked styrene / acrylic resin)>
JSR hollow particles SX866 were used.
When the particles 6 made of resin were used, conductive particles were separately added to the surface layer. Tin oxide particles (manufactured by CIK Nanotech) were used as the conductive particles.

<Preparation of particles 7 (core material = alumina, shell material = tin oxide)>
Regarding the particles 7, in the production of the particles 1, alumina is used instead of the 0.1 μm aluminum borate particles, and the average particle size of the core portion and the average particle size r ₁ of the completed particles shown in Table I are obtained. Other than this, it was produced in the same manner as in particle 1.

<Preparation of particles 11 (core material = tin oxide, shell material = zinc oxide)>
In addition to using tin oxide as the core material in the method for producing the particles 2, the particles 11 were formed until _{the average particle size of the core portion and the average particle size r 1 of the finished particles shown in Table I were reached.} Others were manufactured in the same manner.

<Particle 12 (core material = titanium oxide, shell material = none)>
As the particles 12, titanium oxide MT-500B (average particle size 35 nm) manufactured by TAYCA Corporation was used.

<Preparation of particles 13 (core material = tin oxide, shell material = none)>
Tin oxide (manufactured by CIK Nanotech) was used as the particle 13.

[Surface modification of particles]
Of the particles 1 to 7 and the particles 11 to 13, all the particles other than the particles 6 were surface-modified by the following method and then contained in the surface layer.
When the particles 6 are used in the surface layer, the particles 6 are used without surface modification, but the tin oxide particles used in combination with the particles 6 are surface-modified by the following method.

<Method of surface modification of particles>
First, with respect to 100 parts by volume of the particles to be surface-modified, 15 parts by volume of 3-acryloxypropyltrimethoxysilane (KBM-5103; Shin-Etsu Chemical Industry Co., Ltd.), which is a surface modifier, and a solvent (toluene: isopropyl alcohol =) 400 parts by volume of a 1: 1 (volume ratio) mixed solvent) was mixed and dispersed using a wet media dispersion device, after which the solvent was removed. Subsequently, it was dried at 150 ° C. for 30 minutes to obtain surface-modified particles.

<Measurement of average particle size of particles 1 to 7 and particles 11 to 13>
Particles 1 to 7 and particles 11 to 13 were observed with a scanning electron microscope S-5500 manufactured by Hitachi High-Technologies Corporation at an acceleration voltage of 5 kV and 100,000 times, and 100 particles were randomly observed from the observation field. Particles were extracted. For the 100 extracted particles, "the average value r ₀ of the maximum diameter and the minimum diameter" was calculated, _{and the value obtained by averaging the values r 0} was defined as the average particle size r ₁ of the composite particles. The results are shown as the average particle size r ₁ of the finished particles in Table I.

<Grain size of core>
Regarding the core particle size (average particle size), in the measurement of the average particle size of the particles 1 to 7 and the particles 11 to 13, "particles 1 to 7 and particles 11 to 13" form a surface coating layer. The particles were measured in the same manner except that the particles were replaced with the particles before the preparation.

[Preparation of Intermediate Transfer 1 to Intermediate Transfer 9, Intermediate Transfer 11 to Intermediate Transfer 13]
<Preparation of resin base layers made of PPS, PI, PAI>
(Preparation of resin base layer made of PPS)
100 parts by volume of polyphenylene sulfide resin (E2180; Toray Co., Ltd.), 16 parts by volume of conductive filler (carbon black # 3030B; Mitsubishi Chemical Co., Ltd.), and graft copolymer (Modiper (registered trademark) A4400; Nippon Oil & Fats Co., Ltd.) One volume part and 0.2 part by volume of a lubricant (calcium montanate) were put into a uniaxial extruder and melt-kneaded to obtain a resin mixture.
Next, an annular die having a slit-shaped and endless belt-shaped discharge port was attached to the tip of the single-screw extruder. Then, the obtained resin mixture was extruded into an endless belt shape. Next, the extruded endless belt-shaped resin mixture is extrapolated to a cylindrical cooling cylinder provided at the discharge destination, cooled and solidified to form a seamless cylindrical shape having a thickness of 120 μm, a circumference of 750 mm and a width of 359 mm. A resin base layer for an intermediate transfer body (in the shape of an endless belt) was prepared.

(Preparation of PI resin base layer)
N-Methyl-2-pyrrolidone (NMP) solution of polyamic acid consisting of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and p-phenylenediamine (PDA) ("Euwanis S" (Made by Ube Kosan Co., Ltd., solid content 18% by mass)), and dried oxidation-treated carbon black ("SPECIAL BLACK4" (manufactured by Degussa Co., Ltd., pH 3.0, volatile content: 14.0%)) is added to the polyimide resin solid content. It was added so as to be 23 parts by mass with respect to 100 parts by mass. After dividing this composition into two, using a collision type disperser "GeneusPY" (manufactured by Sinus), the composition is collided at a pressure of 200 MPa and a minimum area of 1.4 mm ² , and the composition is mixed by passing through the path of dividing into two again five times. To obtain a polyamic acid solution containing carbon black.
A polyamic acid solution containing carbon black was applied to the inner surface of a cylindrical mold to 0.5 mm via a dispenser, and rotated at 1500 rpm for 15 minutes to obtain a developing layer having a uniform thickness. Further, while rotating at 250 rpm, hot air at 60 ° C. was applied from the outside of the mold for 30 minutes, and then the mixture was heated at 150 ° C. for 60 minutes. Then, the temperature was raised to 360 ° C. at a heating rate of 2 ° C./min, and further heated at 360 ° C. for 30 minutes to remove the solvent, remove the dehydrated ring-closed water, and complete the imide conversion reaction. After that, the temperature was returned to room temperature and the resin base layer was peeled off from the mold to prepare an endless belt-shaped resin base layer for an intermediate transfer material having a total thickness of 100 μm, a circumference of 750 mm and a width of 359 mm.

(Preparation of PAI resin base layer)
Polyamide-imide varnish (manufactured by Toyo Boseki Co., Ltd., Vilomax (registered trademark) HR-11NN, solvent: NMP, weight average molecular weight of polyamide-imide resin contained: 72,000, number average molecular weight of polyamide-imide resin contained: 1. 90,000) 963.86 g and carbon nanofiber dispersion (manufactured by Ube Kosan Co., Ltd., AMC (registered trademark), 5.0 mass% dispersion, solvent: NMP, average particle size of carbon nanofiber: 11 nm) 36. 145 g was mixed, and the mixture was divided into several portions and defoamed with a rotation / revolution mixer (manufactured by Shinky Co., Ltd., AR-250) to prepare a coating liquid.

The obtained coating liquid was applied to the outer surface of the cylindrical mold with a dispenser, and then rotated to obtain a uniform coating surface. After applying hot air at 60 ° C. from the outside of the mold for 30 minutes, heating was performed at 150 ° C. for 60 minutes, and then firing was performed at 250 ° C. for 60 minutes. Then, the temperature was returned to room temperature (25 ° C.), and the mixture was peeled off from the mold to obtain an endless belt-shaped resin base layer for an intermediate transfer body (thickness: 80 μm, circumference 750 mm, width 359 mm).

[Formation of surface layer of intermediate transfer material 1]
<Preparation of coating liquid for surface layer formation>
Reaction of the following monomer 1 as an acrylic monomer with 75 parts by volume, surface-modified particles 1 with 25 parts by volume, and photopolymerization initiator 1 (Irgacure (registered trademark) OXE02; BASF Japan) with 5 parts by volume. For surface layer formation by dissolving and dispersing 5 parts by volume of the accelerator (KAYACURE EPA Nippon Kayakusha) in MIBK (methyl isobutyl ketone) as a solvent so that the solid content concentration is 10% by volume. A coating solution was prepared.

<Formation of surface layer>
The coating liquid for forming the surface layer is applied onto the outer peripheral surface of the resin base layer by a dipping coating method (coating liquid supply amount: 1 L / min) using a coating device so that the dry film thickness is 6.0 μm. A coating film was formed by the above. This state is referred to as a precursor of the intermediate transfer material immediately before forming the surface layer (immediately before curing). Next, the formed coating film was irradiated with ultraviolet rays as active rays (active energy rays) under the following irradiation conditions to cure the coating film to form a surface layer, and an intermediate transfer body 1 was obtained. The ultraviolet irradiation was performed while fixing the light source and rotating the precursor having the coating film formed on the outer peripheral surface of the resin base layer at a peripheral speed of 60 mm / s.

(Ultraviolet irradiation conditions)
Light source type: 365 nm LED light source (SPX-TA; Eye Graphics)
Distance from the irradiation port to the surface of the coating film: 60 mm
Atmosphere: Nitrogen (oxygen concentration 600ppm)
Irradiation light intensity: 2.2 J / cm ²
Irradiation time (precursor rotation time): 240 seconds

[Formation of surface layers of intermediate transcripts 2-9 and intermediate transcripts 11-13]
In the formation of the surface layer of the intermediate transfer material 1, the average thickness shown in Table II, the acrylic monomer (described as “monomer” in Table II), the types of particles and photopolymerization initiators, and the material type of the resin base layer are used. The surface layer was formed by modification to obtain intermediate transfer bodies 2-9 and intermediate transfer bodies 11 to 13. The monomer 3 used had n of 2.
As for the average thickness of the surface layer, a film thickness profile was prepared, and the thickness was measured at 10 randomly selected parts from the portion having a uniform film thickness, and the average value was used as the average thickness. An eddy current type film thickness measuring device "EDDY560C" (manufactured by HELMUT FISCHER GmbH CO) was used for the thickness measurement.
_{Further, the refractive index n 3} of the surface layer shown in Table II is the refractive index of the resin (that is, the binder resin) constituting the surface layer.

[evaluation]
Hereinafter, the manufactured intermediate transcripts 1 to 9 and 11 to 13 were evaluated in the following (1) and (2).
(1) Stability of measurement by optical sensor (variation value of optical sensor 6σ (E ₁ ) / E ₁ and 6σ (E ₂ ) / E ₂ )
(2) Durability

[(1) Stability of measurement by optical sensor]
<Examples 1 to 5, 7 to 9, Reference Example 6 and Comparative Examples 1 to 3>
As an image forming apparatus, bizhub C558 manufactured by Konica Minolta Co., Ltd. was used. The regular intermediate transfer unit of bizhub C558 was evaluated by replacing only the transfer belt with intermediate transfer bodies 1-9 and 11-13 (see Table III).
The measurement environment was 20 ° C. and 50% RH.

First, after resetting all the histories related to image stabilization of the image forming apparatus, image stabilization was performed. In this state, a blank sheet was printed with the color setting. Printing is performed on 3 sheets of A3 paper at the speed of printing on plain paper, and the optical sensors built into the image forming device (2 for color and 2 for black, both are optical sensors that detect light with a wavelength of 940 nm). The value of the optical sensor was read using (there is). The sampling rate is 10 ms. The optical sensor built into the image forming apparatus can output a voltage value obtained by converting the amount of light into a voltage, and the value of the optical sensor is the value of the voltage. The value of the obtained voltage is proportional to the amount of light.
For the values indicated by each optical sensor when printing an image, the average value indicated by the color optical sensor was determined as E ₁ , and the average value indicated by the black optical sensor was determined as E ₂ . Then, 6 [sigma six times the value of the standard deviation σ of the values indicated by each optical sensor (E _1), calculates the variation based on _{6σ (E 2) (6σ (} E n) / E n), the optical this It was used as an index of the stability of measurement by the sensor. The results are shown in Table IV.

(Evaluation criteria),
◎ best _{(pass): 6σ (E n) /} E n ≦ 0.07
○ good _{(pass): 0.07 <6σ (E n} ) / E n ≦ 0.1
× Not _{(Fail): 0.1 <6σ (E n} ) / E n ≦ 0.15
×× not _{(fail): 0.15 <6σ (E n} ) / E n

In the above 6σ (E _n ) / E _n , n represents 1 or 2.

(About Example 10)
The optical sensors were measured in the same manner as in Example 1 except that the wavelength of the light detected by the two optical sensors in Example 1 was changed to 645 nm, and the stability of the measurement by the optical sensors was evaluated.

The intermediate transcripts used in Examples 1 to 5, 7 to 10 , Reference Example 6 and Comparative Examples 1 to 3 are as shown in Table III.

[Evaluation of durability]
The precursors of the intermediate transcripts 1 to 9 and 11 to 13 and the precursors of the intermediate transcripts 1 to 9 and 11 to 13 immediately before forming the surface layer (immediately before curing) are described below using a Fourier transform infrared spectrometer. The IR spectrum is sampled under the conditions shown, the intensity ratio of the C = C expansion and contraction peak derived from the polyfunctional acrylate as the raw material is measured, the reaction rate of the binder resin constituting the surface layer is measured, and the durability is evaluated. Was done.

The reaction rate was calculated by the following formula.
Reaction rate [%] = 100 × [(C = C expansion / contraction peak height in the coating film immediately before curing)-(C = C expansion / contraction peak height in the surface layer)] / (C = C expansion / contraction in the coating film immediately before curing) Peak height)
The above-mentioned "coating film immediately before curing" is used for forming a surface layer on the outer peripheral surface of the resin base layer in the precursors of the intermediate transferees 1 to 9 and 11 to 13 immediately before forming the surface layer (immediately before curing). It is a coating film formed by applying a coating liquid.
Further, in the above formula, the "surface layer" is a surface layer formed by curing the coating film, and is the surface layer of the intermediate transfer bodies 1 to 9 and 11 to 13 produced as described above. Is shown.

(Evaluation criteria)
◎ (Pass): 90% or more ○ (Pass): 86% or more and less than 90% × (Fail): 82 or more and less than 86% × × (Fail): Less than 82%

[summary]
Examples 1 to 5, 7 to 10 show that according to the present invention, it is possible to stabilize the measurement of the optical sensor for detecting the toner concentration, and to provide an intermediate transfer material having high durability. Was done.
In Example 7, since the composite particles having a slightly small difference in refractive index (| n ₁ −n ₂ |) were used, excellent results were not achieved, but it was shown that the effects of the present invention were sufficiently exhibited. Has been done.

In Comparative Example 1, since particles having no difference in refractive index are used, the effect of stabilizing the measurement of the optical sensor cannot be obtained. It is considered that this is because the particles 11 used in Comparative Example 1 do not scatter and reflect light at the interface between the core portion and the shell because there is no difference in refractive index between the core material and the shell material.
In Comparative Example 2, in particular, a large amount of titanium oxide particles (single layer) having a high refractive index were used. Therefore, in Comparative Example 12, although the measurement of the optical sensor can be stabilized, the reaction rate of the acrylic monomer becomes remarkably low due to the property of the titanium oxide particles to absorb UV light and the photocatalytic activity. Insufficient cross-linking causes insufficient mechanical strength, which in turn causes problems in durability, which is not practical.
Since Comparative Example 3 is a single-layer particle, the effect of increasing the frequency of scattering and reflection of light has not been obtained, and the measurement of the optical sensor cannot be stabilized at all.

210 Intermediate transfer member 210a Resin base layer 210b Surface layer 210c Elastic layer

Claims (9)

An intermediate transfer body used in an image forming apparatus that first transfers a toner image carried on an electrostatic latent image carrier to an intermediate transfer body and then secondarily transfers the toner image from the intermediate transfer body to a recording material. hand,
The intermediate transfer material has an endless belt shape and contains at least a resin base layer and a surface layer.
The surface layer contains a binder resin and composite particles containing a first material and a second material.
The composite particles have a structure in which at least the periphery of the first material is coated with the second material.
The average particle size of the composite particles is in the range of 100 to 300 nm.
As the second material, a conductive material is contained, and the material is contained.
When the refractive index of the first material is n ₁ and the refractive index of the second material is n ₂ , the intermediate transfer product is characterized by satisfying the following relational expressions (1) and (2). ..
n ₁ ≠ n ₂ ... Relational expression (1)
0.30 << n ₁ −n ₂ | ・ ・ ・ Relational expression (2)
[In the above formula, the refractive indexes n ₁ and n ₂ are values measured at the same wavelength in the wavelength range of 500 to 800 nm. ] The intermediate transfer material according to claim 1, wherein the conductive material contains any one of tin oxide, zinc oxide and titanium oxide. When the refractive index n ₃ of the binder resin, the refractive index n ₂ of the first refractive index n ₁ and the second material of the material, satisfy the following equation (3) and equation (4) The intermediate transcript according to claim 1 or 2, characterized in that.
n ₁ <n ₂ ... relational expression (3)
n ₃ <n ₂ ... Relational expression (4) The binding resin contains at least a cured (meth) acrylic resin composed of a structural unit derived from a polyfunctional (meth) acrylic monomer, according to any one of claims 1 to 3. The intermediate transcript of the description. When the refractive index of the resin contained as a main component in the resin substrate was n _4, according to any one of claims 1 to satisfy the following equation (5) to claim 4 Intermediate transcript.
1.6 ≤ n ₄ ... Relational expression (5) The intermediate transfer product according to any one of claims 1 to 5, wherein the resin contained in the resin base layer as a main component is any one of polyimide, polyphenylene sulfide, and polyamide-imide. The average thickness of the surface layer, an intermediate transfer member according to any one of claims 1, wherein the at 6μm or less to claim 6. An image forming apparatus that first transfers a toner image carried on an electrostatic latent image carrier to an intermediate transfer body, and then secondarily transfers the toner image from the intermediate transfer body to a recording material.
The intermediate transfer material according to any one of claims 1 to 7, an optical sensor that detects _{any wavelength λ 1} selected from visible light or near-infrared light of 1000 nm or less, and the like. With
An image forming apparatus comprising a means for measuring the toner concentration on the intermediate transfer body by using the optical sensor. The image forming apparatus according to claim 8 , wherein the average particle size r ₁ of the composite particles and the wavelength λ ₁ satisfy the following relational expression (6).
2 × r ₁ <λ ₁ ... Relational expression (6)

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